There's a sudden release of water and dust as Garn accidentally puts weight on the pressure plate. After a moment, he finds its boundaries and is confident that he can guide everyone safely to the other side -- assuming they follow his directions to the letter.
The door opens with a moment's work: The complex mechanisms aren't particularly successful at keeping even a moderately competent thief from opening the locks.
The room beyond is circular in shape, a crumbling and rat-infested chamber. The ironed-barred door and the cold brick walls give the place the air of some hideous dungeon cell from a nightmare. The room is streaming with dampness and poisonous with stench, due perhaps to the corrupting influence of the filthy water lapping at the group's legs. A statue of a sea-captain stands opposite the door, the figure proud and defiant, with several sahuagin cowed at his feet. Lying in the center of the room is a sarcophagus, its heavy stone lid dust-laden and apparently untouched.
Suddenly, there is a cold draft like someone – or something – passed by, and the sense the presence of an intangible evil.